1. Field of the Invention
The present invention relates to high-precision positioning, more particularly to an actuating apparatus, an actuating system and a method for actuating a working stage to move relative to a platform and capable of high-precision positioning.
2. Description of the Related Art
Linear scales are commonly employed in high-precision measurements of relative positions (relative displacements). Further, the utilization of computer numerical control provides compensation for errors in the measurements that arise from such as backlash of ball screw shafts and servo motors, and hysteresis of piezoelectric actuators. These errors are generally recorded in tables for later reference in corrections of the measured relative positions.
However, linear scales are inherently characterized by cumulative errors associated with the manufacturing process thereof, and typically have an accuracy of ±(3+L/0.2)μm, where L is length in meters. In other words, linear scales are not suitable for use in machining of products of large dimensions (e.g., wind turbine blades of large wind power generators). Moreover, since the relative positions are consecutively measured with linear scales, the errors associated therewith are also cumulative.
Therefore, how to provide a metrological technique/tool that is capable of absolute positioning and that is suitable for use in machining of products of large dimensions has been a subject of interest in the industry.